1. Field of the Invention
Embodiments of the present invention relate to circuitry for supplying power and data, a power and data supply system, methods of supplying power and data, and a hydrocarbon extraction facility.
2. Description of the Prior Art
Conventionally, data communication between a surface location (known as “topside”) and an underwater installation, such as a subsea fluid extraction well, is often achieved by coupling the communication data onto an AC power line, within the cable umbilical, feeding power for the control system to the well subsea tree. In such systems an analogue data waveform is superimposed on the AC power waveform at one end of the umbilical and at the other end, power and data filters are used to separate the power waveform from the data waveform. In this way, the number of lines within the umbilical may be reduced, since dedicated communications and power lines are no longer required in view of the combined communications and power line. The use of such communication on power (COPs) systems is popular when the distance from the surface well control platform and the underwater facility is long (i.e. tens of miles or more), as the saving of copper in the umbilical and thus the cost reduction is substantial. There is a problem however that present systems use hardware filters which need re-designing for every new subsea control system requirement. Furthermore these filters are not accurate, are space intensive due to having to handle large power and they introduce distortions, noise and power losses.
Prior art may be mentioned in U.S. Pat. No. 4,398,178, WO 00/46923, EP 2104240, GB 2441811, WO2004/028064, U.S. Pat. No. 4,173,714, EP0463341.